IC tag

ABSTRACT

The present invention provides an IC tag which has a structure comprising a first adhesive layer formed on a surface of a substrate sheet, an electronic circuit and an IC chip connecting both ends of the electronic circuit, both formed on the surface of the first adhesive layer, and a second adhesive layer covering the electronic circuit and the IC chip. The IC tag further includes a release agent layer formed at positions corresponding to the both ends of the electronic circuit and located at the interface between the substrate sheet and the first adhesive layer. When the IC tag attached to an article is peeled off, the built-in electronic circuit is surely broken.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an IC tag which can break a built-inelectronic circuit when the IC tag attached to an article is peeled off.

2. Description of the Prior Art

By attaching an IC tag to articles such as goods, storage articles andloadings, article managements have been conducted recently. For example,the article management has been conducted by attaching an IC tagrecorded by information such as production condition, stock state, costinformation and used condition to the goods and further confirming theinformation by an interrogator, according to needs.

However, when the IC tag attached to the article is insufficient in theadhesive strength of the adhesive used in the IC tag, the IC tag may bere-attached to another article by any causes such as errors and carelessmistakes. And, the IC tag may be re-attached to another articleintentionally. In such situation, article management can not becorrectly conducted longer.

DISCLOSURE OF THE INVENTION

As the method for solving the problems described above, it is requiredto conduct the article management correctly by damaging the function ofthe IC tag, when the IC tag is re-attached to another article.

As a result of efforts by the present inventors to solve theabove-described problems, it was found that the problems described aboveare achieved by laminating a first adhesive layer on a surface of asubstrate sheet, forming an electronic circuit and an IC chip connectingboth ends of the electronic circuit on the surface of the first adhesivelayer, laminating a second adhesive layer covering the electroniccircuit and the IC chip, and forming a release agent layer at positionscorresponding to the both ends of the electronic circuit and located atthe interface between the substrate sheet and the first adhesive layer.And thus the present invention is completed.

That is to say, the present invention provides an IC tag which has astructure comprising a first adhesive layer laminated on a surface of asubstrate sheet, an electronic circuit and an IC chip connecting bothends of the electronic circuit, both the electronic circuit and the ICchip being formed on a surface of the first adhesive layer, and a secondadhesive layer laminated for covering the electronic circuit and the ICchip, wherein a release agent layer is further formed at positionscorresponding to the both ends of the electronic circuit and located atthe interface between the substrate sheet and the first adhesive layer.

The present invention also provides the IC tag as described above,wherein the release agent layer is formed to cover the range of 20 to 90percents of an area surrounded by an outside circumference of theelectronic circuit through the first adhesive layer.

The present invention also provides the IC tag as described above,wherein a release liner is formed on a surface of the second adhesivelayer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an outline of a cross-section of an IC tag of oneembodiment of the invention;

FIG. 2 shows a plane view of an electronic circuit of one embodiment inan IC tag of the invention;

FIG. 3 shows a plane view of an IC tag of other one embodiment of theinvention;

FIG. 4 shows a cross-section of a state that an IC tag of other oneembodiment of the invention is peeled off;

In drawings, 1 means a substrate sheet, 2 means a first adhesive layer,3 means an electronic circuit, 4 means a second adhesive layer, 5 meansan IC chip, 6 means a release agent layer, and 7 means a release liner.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The IC tag of the invention is explained based on the drawings. FIG. 1shows an outline of a cross-section of an IC tag of one embodiment ofthe invention.

The substrate sheet 1 is preferably a sheet composed of a thermoplasticresin.

As the sheet composed of the thermoplastic resin, for example, thesheets composed of one or more of various synthetic resins, such aspolyolefin resin like polyethylene resins of high density polyethylene,middle density polyethylene, low density polyethylene and the like,polypropylene resins of polypropylene,polymethyl-1-pentene/ethylene/cyclic olefin copolymer, andethylene-vinyl acetate copolymer; polyester resins like polyethyleneterephthalate, polyethylene naphthalate, polybutylene terephthalate;polyvinyl chloride resins; polyvinylalcohol resins; polycarbonateresins; polyamide resins; polyimide resins; fluororesins; copolymerscontaining two or more polymerization units thereof; polymer blendscontaining two or more resins thereof; polymer alloys containing one ormore resins thereof can be used. In particular, the sheets composed ofpolyester resins are preferably used. The substrate sheet 1 may beoriented uniaxially or biaxially. The substrate sheet 1 may be composedof single layer or two or more layers of different layers or samelayers. Also, the substrate sheet 1 has preferably water resistance. Ifthe substrate sheet has water resistance, a damage such as breaking ofthe substrate sheet is not caused when the substrate sheet is wet withwater.

Thickness of the substrate sheet 1 does not have any limitation.However, the thickness is generally in the range of 10 to 250 μm andpreferably in the range of 20 to 100 μm.

For controlling the adhesive strength between the substrate sheet 1 andthe first adhesive layer 2, the surface of the substrate sheet 1 can besurface-treated. The surface-treatment includes, for example, coronadischarge treatment, chemical treatment, resin-coating and the like.

Adhesives used in the first adhesive layer 2 include various adhesivessuch as thermo melting adhesives, pressure-sensitive adhesives andthermosetting adhesives. The kinds of the adhesive include, for example,natural rubber adhesives, synthetic rubber adhesives, acrylic resinadhesives, polyester resin adhesives, polyvinyl ether resin adhesives,urethane resin adhesives and silicone resin adhesives.

Examples of the synthetic rubber adhesives include styrene-butadienerubber, polyisobutylene rubber, isobutylene-isoprene rubber, isoprenerubber, styrene-isoprene block copolymer, styrene-butadiene blockcopolymer, styrene-ethylene-butylene block copolymer, ethylene-vinylacetate thermoplastic elastomer and the like. Examples of the acrylicresin adhesives include homopolymers of monomer such as acrylic acid,methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate,2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butylmethacrylate, and acrylonitrile, or copolymers of 2 or more of monomersthereof. Polyester resin adhesives are copolymers of a polyol and apolybasic acid. The polyol includes ethylene glycol, propylene glycol,and butanediol. The polybasic acid includes terephthalic acid, adipicacid, and maleic acid. Examples of the polyvinyl ether resin adhesivesinclude polyvinyl ether, and polyvinyl isobutyl ether. Examples of thesilicone resin adhesives include dimethyl polysiloxane. The adhesivescan be used singly or in combination of two or more members.

Among the adhesives, the polyester resin adhesives are preferable.

A tackifier, a softener, an antioxidant, a filler, a coloring agent suchas a dye and a pigment or the like can be mixed in the first adhesivelayer 2, according to needs.

The tackifier includes rosin resins, terpene phenol resins, terpeneresins, aromatic hydrocarbon modified terpene resins, petroleum resins,coumarone-indene resins, styrene resins, phenol resins and xyleneresins. The softener includes process oils, liquid rubbers andplasticizers. The filler includes silica, talc, clay, calcium carbonateand the like.

Thickness of the first adhesive layer 2 does not have any limitation.However, the thickness is generally in the range of 3 to 100 μm andpreferably in the range of 5 to 50 μm.

In the IC tag of the present invention, the release agent layer 6 isformed at positions corresponding to the both ends of the electroniccircuit 3 and located at the interface between the substrate sheet 1 andthe first adhesive layer 2.

The release agent layer 6 is formed at positions corresponding to theboth ends of the electronic circuit 3, but is not formed at positionscorresponding to the center section of the electronic circuit 3. Thus,the first adhesive layer 2 is laminated directly on the surface of thesubstrate sheet 1 at positions corresponding to the center section ofthe electronic circuit 3. Therefore, when the IC tag is peeled off afterthe IC tag is attached to the article, the center section of theelectronic circuit 3 is peeled off together with the substrate sheet 1in the state that the center section of the electronic circuit 3 isattached to the first adhesive layer 2, and then the electronic circuit3 is cut. The release agent layer 6 is not needed to cover all ofpositions corresponding to the both ends of the electronic circuit 3.Accordingly, there may be a section at which the release agent layer 6is not covered.

The release agent layer 6 is formed to cover the range of preferably 20to 90 percents, more preferably 40 to 80 percents of an area surroundedby an outside circumference of the electronic circuit 3 through thefirst adhesive layer 2.

The release agent layer 6 is preferably formed as the release agentlayer 6 projects over the outside circumference of the electroniccircuit 3. The width of the projecting area of the release agent layer 6does not have any limitation. However, the width is preferably in therange of not less than 1 mm.

The shape of the release agent layer 6 needs the shape capable to format positions corresponding to the both ends of the electronic circuit 3.The shape of the release agent layer 6 includes preferably triangle,quadrangle, polygons such as pentagon and polygons having more than fiveangles, ellipse and circle (referred to FIG. 2 and FIG. 3). Two shapesof the release agent layer 6 may be same or different. Two of therelease agent layer 6 are preferably separated perfectly andindividually, but may be connected at a part of the release agent layer6.

Release agents used in the release agent layer 6 include, for example,silicone resin, long chain alkyl group-containing resin and fluororesin.

Thickness of the release agent layer 6 does not have any limitation.However, the thickness is preferably in the range of 0.01 to 5 μm andmore preferably in the range of 0.03 to 1 μm.

In the IC tag of the present invention, the electronic circuit 3 isformed on a surface of the first adhesive layer 2.

The electronic circuit 3 is a circuit composed of a conductive material.The conductive material includes, for example, metal simple substancesuch as metallic foil, vapor deposition film and thin film produced byspattering. As the metal simple substance, gold, silver, nickel, copper,aluminium and the like can be used. Also, as the conductive material,conductive pastes produced by dispersing a perticle of metal such asgold, silver, nickel and copper in a binder, can be used.

The average particle diameter of the metal particle is preferably in therange of 1 to 15 μm and more preferably in the range of 2 to 10 μm. Thebinder includes, for example, polyester resins, polyurethane resins,epoxy resins and phenol resins.

Thickness of the layer of conductive material forming the electroniccircuit does not have any limitation. However, the thickness of themetallic foil is preferably in the range of 5 to 50 μm, the thickness ofthe vapor deposition film or metallic film produced by spattering ispreferably in the range of 0.01 to 1 μm and the thickness of conductivepaste is preferably in the range of 5 to 30 μm.

The method for forming the electronic circuit 3 on the surface of thefirst adhesive layer 2, include, for example, a method for forming theelectronic circuit 3 by adhering a metallic foil to the substrate sheet1 with adhesive, etching-treating the metallic foil and then removingsections other than the electronic circuit. The etching-treatment can beconducted by the same treatment as general etching-treatment. Theforming of the electronic circuit 3 to the surface of the first adhesivelayer 2 can be also conducted by adhering the conductive paste in theshape of the electronic circuit 3 to the surface of the first adhesivelayer 2 by means such as printing and application.

The shape of the electronic circuit 3 includes, for example, shapesindicated by FIG. 2 and FIG. 3. In FIG. 2 and FIG. 3, the electroniccircuit 3 as an antenna is formed by arranging a line of conductivematerial in quartet ring having specific space between each lines in thedirection from the outside circumference of a rectangle substrate sheet1 to the inside. The electronic circuit 3 may be arranged in quartetring as indicated in FIG. 2 and FIG. 3, or may be arranged in singletring, doublet ring, triplet ring, or quintet or more ring. The length ofthe electronic circuit 3 can be preferably controlled in a multiple ofthe wavelength of the received electric wave.

The IC chip 5 is connected to both ends of the electronic circuit 3. TheIC chip 5 can be formed inside of the electronic circuit 3, outside ofthe electronic circuit 3, or in the upper portion of the electroniccircuit 3.

In order to connect the ends of most outside ring and most inside ringof the electronic circuit 3 to the IC chip 5, the end of most outsidering or most inside ring of the electronic circuit 3 is preferablyconnected to the IC chip 5 by forming the line (jumper circuit) from theend over the ring electronic circuit 3 in direction of the inside or theoutside of the electronic circuit 3, without short circuit to the ringelectronic circuit 3.

The method for forming the jumper circuit includes a method for forminga conductive circuit line by printing insulating ink in line crossingthe portion of the ring electronic circuit 3 from the end of theelectronic circuit 3 by screen printing or the like, and then printingconductive paste in line on the printed insulating ink by screenprinting or the like. The conductive paste includes that describedbefore. The insulating ink includes light curable ink such asultraviolet curable ink.

The method for connecting the IC chip 5 to the end of the electroniccircuit 3 includes a method for connecting by forming an anisotropicconductive film on the surface of the end of the electronic circuit 3and then connecting flip-chip bonding method via the anisotropicconductive film. The flip-chip bonding method is a method for conductingeasily between the end of the electronic circuit 3 and the IC chip 5 byforming a wire bump to an electrode portion of the IC chip 5, andpressing the surface of the wire bump formed on the IC chip 5 to theanisotropic conductive film covered on the surface of the end of theelectronic circuit 3 so that the wire bump insert in the anisotropicconductive film.

In the IC tag of the present invention, the second adhesive layer 4 islaminated to cover the electronic circuit 3, the IC chip 5 and thesurface of the first adhesive layer 2 that the electronic circuit 3 isnot formed.

Adhesives used in the second adhesive layer 4 include various adhesivessuch as thermo melting adhesives, pressure-sensitive adhesives andthermosetting adhesives. The kinds of the adhesive include, for example,the same as adhesives used in the first adhesive layer 2, as describedbefore.

The adhesives can be used singly or in combination of two or moremembers. Among the adhesives, the pressure-sensitive adhesives arepreferable and acrylic pressure-sensitive adhesives are more preferable.

The surface of the second adhesive layer 4 is preferably flat.

Thickness of the second adhesive layer 4 does not have any limitation.However, the thickness of the portion covering the electronic circuit 3and the IC chip 5 is different from the thickness of the portioncovering the first adhesive layer 2. Maximum thickness is normally inthe range of 10 to 100 μm and preferably in the range of 15 to 50 μm.

The surface of the second adhesive layer 4 can be covered with therelease liner 7.

As the release liner 7, any release liners can be used. For example,release liners in which release treatment is conducted to the surface ofthe substrate to be contacted to the second adhesive layer 4 accordingto needs, can be used. As the substrate, films composed of variousresins such as polyethylene terephthalate, polybutylene terephthalate,polyethylene, polypropylene and polyarylate, and various paper materialssuch as papers laminated with polyethylene, papers laminated withpolypropylene, clay-coated papers, resin-coated papers and glassinepapers are illustrated.

In the case, representative examples include a formation of releaseagent layer composed of release agent such as silicone resin, long-chainalkyl group-containing resin and fluororesin.

The thickness of the release liner 7 does not have any limitation.However, the thickness can be decided properly.

The second adhesive layer 4 can be formed by applying directly to theelectronic circuit 3, the IC chip 5 and the surface of the firstadhesive layer 2 in which the electronic circuit 3 is not formed.Further, after the second adhesive layer is formed by applying theadhesive on the surface of the release agent layer of the release liner7, the second adhesive layer can be attached to the electronic circuit3, the IC chip 5 and the surface of the first adhesive layer 2 in whichthe electronic circuit 3 is not formed.

Methods for forming the first adhesive layer 3, the second adhesivelayer 4 and the release agent layer 6 do not have any limitation, andvarious methods can be used. The methods include, for example, air knifecoater, brad coater, bar coater, gravure coater, roll coater, curtaincoater, die coater, knife coater, screen coater, Mayer bar coater andkiss coater.

When the IC tag is peeled off from the article after the IC tag isattached to the article, the substrate sheet 1 is peeled off at theinterface against the release agent layer 6 formed to cover theelectronic circuit 3, and the substrate sheet 1 without the releaseagent layer 6 at the center section of the electronic circuit 3 ispeeled off at the interface between the article and the second adhesivelayer 4 in the state that the second adhesive layer 4, the electroniccircuit 3 and the first adhesive layer 2 are attached to the substratesheet 1, as indicated in FIG. 4. As the result, the electronic circuit 3is cut.

When the end portion of the substrate sheet 1 is attached directly tothe first adhesive layer 2, the end portion of the substrate sheet 1 maybe peeled off at the interface of the substrate sheet 1 and the firstadhesive layer 2, or may be peeled off in the layer of the firstadhesive layer 2. When the width of the first adhesive layer 2 attacheddirectly to the end portion of the substrate sheet 1 is short, it ispreferable because the substrate sheet 1 is peeled off easily at theinterface between the substrate sheet 1 and the first adhesive layer 2.

EXAMPLES

The present invention will be explained by an example more concretely inthe next paragraph. In addition, the present invention was notrestricted at all by these examples.

Example 1

A release agent layer 6 was formed by applying a silincone resin releaseagent in the shape as indicated in FIG. 2 (having angle of the obliqueline in trapezoid of 45°, width of unapplied portion of 3 mm, areacovered with two trapezoids and surrounded by an outside circumferenceof the electronic circuit of about 75 percents of area surrounded by anoutside circumference of the electronic circuit, and space lengthbetween the end of trapezoid and the substrate sheet 1 of 1 mm), on onesurface of polyethylene terephthalate film (having width of 28 mm,length of 12 mm and thickness of 50 μm) in an amount to form the driedthickness of 0.05 μm and then curing at 130° C. for 1 minutes. Next,polyester type thermo melting adhesive (produced by TOYO BOSEKI CO.,LTD., trade name “BAYRON 30SS”) was applied on the surface of therelease agent layer 6 and the substrate sheet 1 by gravure coater inamount to form the dried thickness of 5 μm to laminate the firstadhesive layer 2. Further, on the surface of the first adhesive layer 2,an electrolytic copper foil having thickness of 35 μm was heated andpressed by heat seal roll of 100° C. Next, on the surface of theelectrolytic copper foil, etching resist ink was printed in quintet ringelectronic circuit (antenna) having long side of 25 mm, short side of 6mm and line width of 0.3 mm by screen-printing method, as indicated inFIG. 2. The printed electrolytic copper foil was etching-treated with asolution of ferric chloride to remove the portion other than thecircuit. And then, the etching resist ink was removed with an aqueousalkali solution to form the electronic circuit 3.

In order to conduct the end of most inside ring of the electroniccircuit 3 (antenna) and the end of most outside of the electroniccircuit 3, an ultraviolet curable ink was printed to the space betweenthem in line shape by screen printing method. And then, ultravioletlight was irradiated to cure the ultraviolet curable ink. Next, a silverpaste (average particle diameter of silver particle of 5 μm, binder ofpolyester resin) was printed in line shape (having length of 10 mm) onthe surface of the cured line of the ultraviolet curable ink, and driedto form the jumper circuit.

Next, a wire bump was formed at the electrode portion of an IC chip 5(produced by PHILIPS CO., trade name of “I/CODE”) with a gold wire. TheIC chip 5 was connected to the both ends of the circuit through ananisotropic conductive film (produced by SONY CHIMICAL CO., LTD., tradename of “FP2322D”) by using the flip chip bonding method.

On the other hand, a release paper having the second adhesive layer 4was prepared by applying an acrylic pressure-sensitive adhesive havinglow adhesive strength (produced by LINTEC CORPORATION, trade name of“PA-T1”) on the release-treated surface of the release paper obtained byrelease-treating all surface of one side of a glassine paper havingthickness of 70 μm with silicone resin by using roll knife coater, anddrying to form the second adhesive layer 4 having thickness of 20 μm.

Next, by attaching the second adhesive layer 4 in the release paper withthe second adhesive layer 4 to all of the surface forming the electroniccircuit 3 and the IC chip 5 of the substrate sheet 1, the secondadhesive layer 4 was covered on the first adhesive layer 2, theelectronic circuit 3 and the IC chip 5 to prepare the IC tag.

The obtained IC tag was tested by non-contact transmitting and receivingtest. At the result, the transmitting and receiving could be conductedcorrectly.

The all surface-treated release paper in the IC tag was peeled off, andthe IC tag was attached to a polypropylene resin plate. After 24 hours,the IC tag was peeled off from the polypropylene resin plate. Theportion of the electronic circuit 3 covered with the release agent layer6 was remained on the polypropylene resin plate. The portion other thanthe release agent layer 6 was peeled off from the polypropylene resinplate together with the polyethylene terephthalate sheet of thesubstrate sheet 1. According to the peeling, the electronic circuit 3was cut. The peeled IC tag was tested by non-contact transmitting andreceiving test. At the result, the transmitting and receiving could benot conducted.

Comparative Example 1

The IC tag were prepared in the same method as described in Example 1except that the release agent layer 6 was not formed. The obtained ICtag was tested by non-contact transmitting and receiving test. At theresult, the transmitting and receiving could be conducted correctly.

The IC tag was attached to the polypropylene resin plate and peeled offin the same method as described in Example 1. The IC tag could be peeledoff easily and the electronic circuit 3 was not broken. The peeled ICtag was tested by non-contact transmitting and receiving test. At theresult, the transmitting and receiving could be conducted correctly.

When the IC tag attached to an article is peeled off, the built-inelectronic circuit can be surely broken.

1. An IC tag which has a structure comprising a first adhesive layerlaminated on a surface of a substrate sheet, an electronic circuit andan IC chip connecting both ends of a line of the electronic circuit,both the electronic circuit and the IC chip being formed on a surface ofthe first adhesive layer, and a second adhesive layer laminated forcovering the electronic circuit and the IC chip, wherein a release agentlayer is further formed at positions corresponding to both separated endsections of the electronic circuit and located at the interface betweenthe substrate sheet and the first adhesive layer, but is not formed atpositions corresponding to the center section of the electronic circuit,wherein the release agent layer is formed to cover a range of 20 to 90percent of an area surrounded by an outside circumference of theelectronic circuit throughout the first adhesive layer such that theelectronic circuit is rendered electrically inoperable when thesubstrate is peeled off from the IC tag.
 2. The IC tag as claimed inclaim 1, wherein a release liner is formed on a surface of the secondadhesive layer.
 3. The IC tag as claimed in claim 1, wherein the releaseagent layer is formed of a silicone resin, a long chain alkylgroup-containing resin, or a fluororesin.
 4. An IC tag comprising: afirst adhesive layer laminated on a surface of a substrate sheet; anelectronic circuit; an IC chip connecting both ends of a line of theelectronic circuit, both the electronic circuit and the IC chip beingformed on a surface of the first adhesive layer; a second adhesive layerlaminated for covering the electronic circuit and the IC chip; and ameans for rendering the electronic circuit electrically inoperable whenthe substrate sheet is peeled off from the IC tag adhered to anadherend, said means including a release agent layer formed at positionscorresponding to both separated end sections of the electronic circuitand located at the interface between the substrate sheet and the firstadhesive layer, but not formed at positions corresponding to the centersection of the electronic circuit.